Verti-Block wall built for a slope repair along Highway 101 in Oregon

Application guide

Verti-Block for highway and roadway retaining walls

Roadway widening, slope repair and interchange walls, built on a tight schedule inside a tight right-of-way.

  • 3 min read
  • 8 sections
  • Updated

The short answer

Verti-Block suits roadway widening, slope repair and interchange walls because it is set dry by excavator with no forms, rebar or cure time, builds gravity walls up to 19 ft in good soils where the right-of-way leaves no room for geogrid, and is designed to NCMA and AASHTO LRFD with drainage built into the section.

Planning data, not a wall design. Every retaining wall needs a site-specific design by a licensed engineer. We draft free preliminary designs, and a licensed PE reviews and stamps the final design on approval.

Natrix Precast, licensed Verti-Block manufacturer · Vancouver, WA

Verti-Block standard unit: stone-textured face, hollow core and two cast-in lift loops
This is Verti-Block. One standard unit: 2 ft high, 4 ft wide, 3 ft deep, about 1,760 lb.

Meet the block

One big block, set by machine

Verti-Block is a hollow-core precast concrete block with a stone-textured face. An excavator sets each unit, raised lugs lock it to the course below, and crushed stone in the core adds weight and drains the wall from top to bottom.

Diagram of a Verti-Block unit: cast-in lift loops for machine setting, a hollow core filled with crushed stone, the stone core draining the full wall height, and raised lugs that lock into the notch under the block above
  • 2 × 4 × 3 ftStandard unit: 8 sq ft of wall face
  • ~1,760 lbEmpty; about 3,035 lb with stone in the cores
  • 5.5–19 ftPublished gravity heights, no geogrid
  • 304 sq ftWall face per truckload
Verti-Block wall with an outside corner and a curve around a lawn
Corners and curves
Verti-Block wall with stairs beside a modern home
Stairs and height steps
Stepped Verti-Block wall along a fence line
A top of wall that follows the grade
Tiered, curving Verti-Block wall on a hillside
Tiered walls

What roadway walls have to get right

  • Schedule: every day of a lane closure or detour costs money and goodwill.
  • Right-of-way: walls often sit tight against property lines, utilities and existing pavement, with no room to excavate a reinforced zone.
  • Drainage: roadway runoff and Pacific Northwest rain put water behind the wall.
  • Durability: freeze-thaw cycles, deicing and decades of service.
  • Review: a design the agency can check against published standards.

Set, not poured

A Verti-Block wall goes in dry. Units are set by excavator with a block grab, and each course locks onto the one below through a male/female connection that sets the batter automatically. There are no forms to build, no rebar to tie, and no cure time before backfilling. In our experience, a crew sets about 450 sq ft of wall face per day, so walls go in over days rather than weeks.

Hollow cores also cut deliveries into a work zone: each truckload carries 304 sq ft of wall face, about double the face area per haul compared with solid large-format block.

  • NoneNo forms, no rebar, no cure time before backfill
  • ~450 sq ftWall face set per crew-day, in our experience
  • 304 sq ftWall face per truckload

Gravity walls inside the right-of-way

When there is no room to excavate behind the wall for geogrid, height has to come from the wall itself.

A 14 ft Verti-Block gravity wall with a mass-extender base and a 3 to 7 ft footprint, leaving land back between the wall and the property line
The wall is the footprint. A gravity wall with a mass-extender base needs 3 to 7 ft, with no reinforced zone behind it. Illustration only.

Verti-Block's published gravity heights, with mass-extender base courses at the standard 5° batter:

Published gravity wall heights, no geogrid
Retained soilLevel, no surchargeLevel, 250 psf surcharge2:1 sloping backfill
Sandy (≥ 30°)7.5 to 15 ft5.5 to 11 ft5.5 to 9.5 ft
Gravelly sand (≥ 35°)9.5 to 17 ft7.5 to 15 ft9.5 to 15 ft
Gravelly (≥ 40°)11 to 19 ft9.5 to 17 ft11 to 17 ft

Mass extenders (48 to 84 in. deep, up to about 5,100 lb) put weight in the base courses where the overturning force is greatest, and they typically backfill with compacted native soil. Laying courses back with the 12-inch setback raises the published gravity height to 24.5 ft in gravelly soil. Full tables, including silty soils, are in the Verti-Block design data.

Taller walls with geogrid

Where there is room for reinforcement, published geogrid designs reach 30 ft and beyond, with Stratagrid in every course at 2 ft spacing and one grid length top to bottom. Grid connects by friction (detail M-03) or positively, looped through the hollow core (detail WD-36).

Geogrid wall section with grid at 2 ft spacing reaching about 0.7 times the wall height on level ground, plus friction connection M-03 and positive connection WD-36 details

Drainage and durability

Wall section numbered with the four drainage details: internal stone drainage column, base collection pipe, geotextile filtration, and surface grading away from the wall
  • Full-height drain: clean crushed stone in the cores (ASTM D448, no more than 5% passing the No. 200 sieve) drains the wall from top to bottom.
  • Base pipe: 3 in. minimum perforated PVC or HDPE in the bottom cavity, or with 12 in. of gravel behind the wall where flows demand it (detail WD-16).
  • Filter fabric: needle-punched non-woven geotextile, 120 lb minimum grab tensile (ASTM D4632), lapped 6 in.
  • Freeze-thaw: units made to ASTM C666 or an approved DOT mix.

Design standards and agency review

Published tables use NCMA (3rd Edition) and AASHTO LRFD methodology. The free Verti-Block analysis software designs to AASHTO ASD and LRFD, NCMA and CAN-CSA, runs seismic and global-stability checks, and produces block counts, geogrid schedules and CAD output for plan sets. Because approvals vary by agency, check your agency's current qualified products list; we can send reviewers the design manual, the referenced details and the design calculations for your wall.

Example: Highway 101 slope repair, Oregon

Natrix supplied Verti-Block for a slope repair along Highway 101 in Oregon. Big units set by machine got the slope stabilized quickly on a tight site. See the project photos.

Tall Verti-Block wall beside a gravel access road at the Highway 101 slope repair
Highway 101 slope repair, Oregon.
Verti-Block wall running along the base of a wooded slope at the Highway 101 repair
The finished wall along the base of the slope.

From plan sheet to stamped design

  1. Send us the site: the plan and profile, the wall line, and any geotechnical data you have.
  2. We draft a preliminary design: block counts, mass-extender layout, geogrid requirements if needed, and a budget number.
  3. Stamped on approval: a licensed PE reviews and stamps the final design for submittal.
  4. Supply: block is cast and stocked in Vancouver, WA and delivered across Washington and Oregon, to whichever contractor wins the bid.

Source: Verti-Crete Design Manual, Release 4.1, Verti-Block product data sheets, and Natrix Precast project experience (marked "in our experience").

In the field

Highway 101 Repair, Verti-Block retaining wall

Commercial & Civil · Highway slope repair

Highway 101 Repair

A Verti-Block repair along Highway 101 in Oregon. Big units set by machine got the slope stabilized quickly on a tight site.

View project →
Sound Wall, Verti-Block retaining wall

Commercial & Civil · Roadside sound / retaining wall

Sound Wall

A roadside Verti-Block wall that screens a home from traffic, giving it privacy and a finished stone look from the street.

View project →

FAQ

Common questions

Is Verti-Block designed to AASHTO?

Yes. The published design tables use NCMA (3rd Edition) and AASHTO LRFD methodology, and the free Verti-Block analysis software designs walls to AASHTO ASD and LRFD, NCMA and CAN-CSA, with seismic and global-stability checks.

Can a Verti-Block wall handle traffic loads above it?

The published gravity tables include a level 250 psf surcharge case, with heights from 5.5 ft to 17 ft depending on soil. Actual traffic, barrier and impact loads are designed for each project in the analysis software and confirmed by the engineer of record.

How fast does a Verti-Block wall go in?

In our experience, a crew sets about 450 sq ft of wall face per day, and walls go in over days rather than weeks, because there is no forming, rebar or cure time. Actual production depends on access, height and site conditions.

Is Verti-Block freeze-thaw durable?

Units are made to ASTM C666 freeze-thaw requirements or an approved DOT mix, and the stone-filled core keeps water draining out of the wall rather than sitting behind it.

Is Verti-Block on our agency's approved products list?

Approvals vary by agency and change over time, so check your agency's current qualified products list. Contact us and we will send what your reviewers need: the design manual, details and design calculations for your wall.

Get a free preliminary wall design.

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